"They do it to please the lady of the house, to look good," said Milton Pitts, the "barber to the presidents" who has coiffed Richard Nixon, Gerald Ford, George Bush and Ronald Reagan, but not Bill Clinton.

"It's sort of like Hamburger Helper. It stretches what you've got a little bit further," said 50-year-old Rep. John Mica, R-Fla., who has sported a toupee nearly half his life. "I think I look better and feel better. And it keeps my head warm."

Some, of course, claim to do it for career reasons, particularly broadcasters whose large salaries depend on the tastes of fickle viewers.

What may be good for NBC weatherman/funnyman Willard Scott (bowling ball bald some days, hirsute others) may not work for the likes of Donaldson, who wears what barber Pitts calls "a small patch in the front, not a whole toupee."

Donaldson, 59, who has built a career on tough grilling of public officials from the White House lawn to "This Week With David Brinkley," had a terse no-comment on his hair.

But occasionally, he has gotten as good as he gives.

During a spirited discussion with Sen. Fritz Hollings, D-S.C., about the 1990 budget agreement, Donaldson suddenly switched gears to zero on what he considered his guest's sartorial hypocrisy.

"Senator, you're from the great textile-producing state of South Carolina. Is it true you have a Korean tailor?"

Yes, Hollings admitted, pointing out that the suit in question was made with American fabric. Then, he added, ". . . if you want to personalize this thing - where did you get that wig, Sam?"

The great interrogator did not answer, then or now.

"It's the only time I've ever seen Sam speechless," said a colleague who asked not to be identified for fear of incurring Donaldson's wrath.

Hollings, who is both snowy of mane and sharp of tongue, said he was only guessing that Donaldson wore a wig but added impishly, "I've never been invited back."

CNN's King has a slightly different problem - hair so thin on top that bright studio lights bounce off the crown. And so each morning, while he gets his hair styled and fluffed, King also gets the top of his head tinted.

Sometimes the coloring agent is a dark paste "that comes in a tin like shoe polish and is applied with a sponge," said one who is familiar with King's grooming habits. Sometimes it is a dark brown goo called "Couvre," French for cover. It is made (where else?) in Beverly Hills.

But don't think for a moment that King, who asks all sorts of important people all sorts of pointed questions, wants to talk about his own tresses or tints.

These newsmen have little on the newsmakers they question, however, and on Capitol Hill there are two names that invariably arise during any discussion of hair: Thurmond and Roth.

At age 90, Thurmond, R-S.C., is still vain about his hair, as befits a man who twice married Southern beauty queens half his age. (He outlived the first and is separated from the second.)

At a recent birthday bash for Thurmond - who seems to have had as many hair colors in the carrot-to-cordovan range over the years as Italy has had governments - former Senate Majority Leader Howard Baker recalled their first meeting.

"When I came to the Senate in '66, Sen. Thurmond was 64 and didn't have quite as much hair."

No lie. Thurmond had a series of hair transplants in the 1970s "because it makes you look better."

Sen. Joe Biden, D-Del., hit the transplant trail a decade later, as he obliquely noted in his Thurmond salute: "When I came to the Senate in '72, you were 70; and I want to tell you I resent any reference to your hair. You have been an inspiration to me in so many ways."

Former Sen. William Proxmire, widely hailed as the Senate's transplant trailblazer despite Thurmond's assertion to the contrary, also flatly refused to discuss his hair.

Small wonder. Plugs don't seem to get much respect.

"When you run your hand over a transplant, it feels like Braille," said barber Pitts.

"Chia hair," sniffed Georgetown salon owner Fernando Sacaluga, referring to the clay animals that sprout wispy green leaves between their ridges. "The trouble is that most men don't want to go to the trouble or expense of getting enough plugs."

But Republican lobbyist Roger Stone is not most men. He spent two years and somewhere between $6,000 and $8,000 on his transplants and now boasts a heroic pompadour where once there was only shiny forehead and scalp.

"To be done properly, it has to be done over a long period of time," said Stone, noting that countless plugs containing up to 25 strands each of his brown hair were moved from the back and sides to the top of his head.

Plugs will only work, of course, if there is sufficient hair to move from point A to point B. And because transplants can be costly, uncomfortable, physically impossible or simply too embarrassing to explain, many men prefer toupees.

On Capitol Hill, nearly all discussions of hairpieces begin or end with Roth, the Delaware Republican, whose silvery toupee was described by one observer as "looking like a slab of veal" and by Pitts, the barber, as "second only to Howard Cosell, who has the worst wig in the world."

"I don't think I have anything to say about that," Roth declared when the subject of politicians' hair was broached.

Sen. Thad Cochran, R-Miss., whose hair turned white while he was in his 40s, once tried Grecian Formula to darken it "but it was so greasy I couldn't stand it."

Sen. Robert Byrd, D-W.Va., likewise seems to have quit using whatever rinse or potion turned his distinguished white hair various shades of blue and lavender.

The House claims several wig-wearers including Mica, who gets a new one every six to 12 months from a Maitland, Fla., barber "because they wear out." Average cost? About $350.

Although Pitts contended that a "really good wig" should cost in the neighborhood of $1,500, the notoriously frugal Mica insisted, "I'd die before I'd pay that."